DESCRIPTION The development of rehabilitative technologies that restore lost neural function by interfacing with the central nervous system is a unique interdisciplinary endeavor. A successful neuroprosthetic device requires a system that can be 1) implanted in the brain for an extended duration, 2) simultaneously record the activities of many neurons, and 3) pass external or intrinsic signals across the skin. Although implant systems based on the Utah Electrode Array (UEA) have satisfied these conditions in chronic animal preparations, improvements are needed in this system before it can be considered for potential human experimentation. The research tasks described in this proposal 1) develop new protocols to more sensitively evaluate the long-term bio-competitively of the UEA, 2) study the effect of increasing the number of electrical connection to the UEA on its biocompatibility, and 3) investigate new technologies to develop high- density percutaneous connectors. The chronic recording capabilities and in vivo biocompatibility of the modified implant system are evaluated in both feline and primate implants. To demonstrate the applicability of this implant system in a neuroprosthetic device, the primate subjects will perform motor behaviors where they will be required to control the position of a cursor on a screen using signals derived from the activities of large groups of neurons in primary motor cortex. These experiments will provide valuable information to further prepare us for the use of the UEA in human experiments to be performed in the near future.